Astronomy Archives

May 11, 2009December 24, 2015 by Fraser Cain

What is the Largest Galaxy?

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Galaxies can range in size from having just a few million stars to well over a trillion stars. But have you ever wondered, what’s the largest galaxy in the Universe. The Universe is a big place, and we’ll probably never be able to see every single galaxy. So we can never know for sure what the biggest galaxy is. Instead, we’ll have to go with, what’s the largest galaxy that we know of?

The largest galaxies in the Universe are the giant elliptical galaxies. These are large, egg-shaped galaxies with trillions of stars. They’re formed through multiple collisions between smaller spiral galaxies of similar size. For example, when our own Milky Way collides with the same sized Andromeda Galaxy in a few billion years, the outcome will probably be a giant elliptical galaxy, with about a trillion stars.

The galaxies that can get the largest are the ones at the very center of galaxy clusters. Astronomers call these cD galaxies (for giant diffuse galaxies), or bright cluster galaxies. The grow by gobbling up any galaxy that comes too close to them, and since they’re at the center of a galaxy cluster, many galaxies get too close. In fact, these galaxies have a large space around them where astronomers can’t find any smaller galaxies; they’ve all been consumed by the larger galaxy.

A large cD galaxy can be 10 times brighter than the Milky Way, with about 100 times as much mass. They can have a diameter of 6 million light-years across (the Milky Way is about 100,000 light-years across).

An example of this is the central galaxy in the cluster Abell 2029.

It’s probably that there are even larger galaxies out there. And if they are there, you’ll find them at the center of the largest galaxy clusters.

We have written many articles about galaxies for Universe Today. Here’s an article about research into the galaxy cluster Abell 2029.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 11, 2009December 24, 2015 by Fraser Cain

Ring Galaxy

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There are spiral galaxies and elliptical galaxies, but one of the strangest you’re ever going to see is a ring galaxy. One of the most famous examples of these is Hoag’s Object, discovered in 1950 by Art Hoag – but there are other examples as well.

And a ring galaxy really does look like a ring. There’s a bright central core, and then a large gap without much luminous matter, and then a bright ring containing hot, blue stars.

Astronomers think that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. The space between stars in a galaxy is vast, so when galaxies collide, the stars don’t actually crash into each other. Instead, it’s their gravity that makes a mess. In this situation, it’s thought that the smaller galaxy slices right through the disk of the larger galaxy. The gravity of the smaller galaxy collapses vast clouds of gas and dust, and creates a burst of star formation around the edge of the larger galaxy.

The change in gravity drastically affects the orbit of the stars in the larger galaxy. They orbit outward and bunch up into the bright starforming ring. This blue ring is continuing to expand outward, and astronomers believe that it only lasts for a few hundred million years before it begins disintegrating. Eventually only the bright galaxy core will remain.

In 2004, astronomers released an image of the ring galaxy AM 0644-741 to celebrate 14 years of service by the Hubble Space Telescope.

We have written many articles about galaxies for Universe Today. Here’s an article about a ring galaxy imaged by Hubble.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 11, 2009December 24, 2015 by Fraser Cain

Comet Galaxy

Galaxy cluster Abell 2667. Image credit: Hubble

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The “Comet Galaxy” is actually just one galaxy located in a distant galaxy cluster known as Abell 2667, located about 3.2 billion light-years away. A recent photograph captured by the Hubble Space Telescope showed this galaxy being torn apart into a comet shape by the intense gravity of galaxy cluster – and that’s how it got the nickname as the Comet Galaxy.

The observation of the Comet Galaxy and the rest of the galaxies in Abell 2667 helped astronomers understand why many galaxies are “gas poor”. Our own Milky Way has tremendous stores of gas and dust which are used for star formation. But other galaxies out there have very little gas which can be used for star formation.

The image of the Comet Galaxy by Hubble helped show that huge gravitational interactions between galaxies in massive clusters cause tremendous damage to the structure of a galaxy, and the amount of gas they have. Galaxies near the center of clusters experience the most damage of all, which galaxies at the outskirts are relatively unharmed. The galaxy collisions can distort the shape of galaxies, and even fling out “homeless stars” into intergalactic space.

Even though the Comet Galaxy’s mass is slightly greater than the Milky Way, it will lose all its gas and dust, and so not be able to generate stars later in life. It will become a gas-poor galaxy with an old population of red stars.

Because the Comet Galaxy is 3.2 billion light-years away, it can only really be seen with the Hubble Space Telescope. Even a powerful backyard telescope wouldn’t be able to locate it.

We have written many articles about galaxies for Universe Today. Here’s a news release from the Hubble Space Telescope about the Comet Galaxy.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 11, 2009December 24, 2015 by Anne Minard

Unusual Cargo Headed to Hubble: A Basketball?

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Most people know Edwin Hubble as a famed astronomer, but he also starred as a forward on the University of Chicago Maroons’ Big Ten champion basketball teams of 1907–08 and 1908–09.

And as fellow Chicago alumnus John Grunsfeld has prepared for his fifth space shuttle flight since 1995, he’s been pondered how best to deflate a century-old ball that Hubble had tossed around in a 1909 victory against Indiana University.

The challenge: Find a way to compactly stow the old pigskin, which to everyone’s surprise lacks an air valve, aboard the space shuttle Atlantis for its upcoming launch.

The problem unfolded last summer in a series of e-mails between Grunsfeld and Michael Turner, a University of Chicago astronomy and astrophysics professor.

“It’s a cosmic mystery as to how the ball was filled, and now for me how to drain it,” Grunsfeld told Turner, who had borrowed the basketball from the university’s athletics program for its orbital flight. Grunsfeld plans to return the basketball personally to the University after the mission, when it will go on display.

“We couldn’t find a valve to deflate it, so we will leave it to the rocket scientists to figure out how to flatten it,” Turner told Grunsfeld. It presented another challenge of the kind that Grunsfeld relishes, but would never have anticipated as an astronaut.

Five weeks before scheduled launch, Grunsfeld punctured the basketball with a hypodermic needle. “Nothing happened, no air hissing out, or any air transfer at all as I compressed the ball,” he said. Grunsfeld assumed that he had punctured the pigskin, but not the underlying air bladder. And yet more punctures with different needles in different locations also failed to deflate the ball.

Finally, with the University’s permission, Grunsfeld resorted to cutting a small incision into the ball. “To my astonishment, I discovered that there is no bladder, and no pressurized air. The basketball was filled with an organic fiber packing,” he said.

Grunsfeld plans to reshape the ball while in orbit and gently pass it around to crewmates during a photo-op. The moment should provide a memorable, light-hearted counterpoint to his usual orbital workload of marathon spacewalks and Hubble Telescope repairs.

Source: Steve Koppes, University of Chicago

May 11, 2009December 24, 2015 by Anne Minard

Milky Way Dwarf Galaxies Thwart Newtonian Gravity?

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Here at Universe Today, the subject of Newtonian gravity always seems to lead to vigorous debate. Now, there’s new research to stoke it.

Manuel Metz, and astrophysicist at the German Aero-space Center, and his colleagues say dwarf galaxies in the Milky Way are arranged in a way that precludes the existence of dark matter — but also depends on it.

“Maybe Newton was indeed wrong,” said Pavel Kroupa, an astronomer at Bonn University. “Although his theory does, in fact, describe the everyday effects of gravity on Earth, things we can see and measure, it is conceivable that we have completely failed to comprehend the actual physics underlying the force of gravity.”

As modern cosmologists rely more and more on the ominous “dark matter” to explain otherwise inexplicable observations, much effort has gone into the detection of this mysterious substance in the last two decades, yet no direct proof could be found that it actually exists. Even if it does exist, dark matter would be unable to reconcile all the current discrepancies between actual measurements and predictions based on theoretical models. Hence the number of physicists questioning the existence of dark matter has been increasing for some time now. Competing theories of gravitation have already been developed which are independent of this construction. Their only problem is that they conflict with Newton’s theory of gravitation.

In two new studies, Metz and his team have examined so-called “satellite galaxies.” This term is used for dwarf galaxy companions of the Milky Way, some of which contain only a few thousand stars. According to the best cosmological models, they exist presumably in hundreds around most of the major galaxies. Up to now, however, only 30 such satellites have been observed around the Milky Way, a discrepancy in numbers which is commonly attributed to the fact that the light emitted from the majority of satellite galaxies is so faint they remain invisible.

A detailed study of these stellar agglomerates has revealed some astonishing phenomena: “First of all, there is something unusual about their distribution,” Kroupa said, “the satellites should be uniformly arranged around their mother galaxy, but this is not what we found.” More precisely, all classical satellites of the Milky Way – the eleven brightest dwarf galaxies – lie more or less in the same plane, they are forming some sort of a disc in the sky. The research team has also been able to show that most of these satellite galaxies rotate in the same direction around the Milky Way, like the planets revolve around the Sun.

The physicists believe that this phenomenon can only be explained if the satellites were created a long time ago through collisions between younger galaxies.

“The fragments produced by such an event can form rotating dwarf galaxies,” Metz said. But there is an interesting catch to this crash theory, “theoretical calculations tell us that the satellites created cannot contain any dark matter.” This assumption, however, stands in contradiction to another observation. “The stars in the satellites we have observed are moving much faster than predicted by the Gravitational Law. If classical physics holds this can only be attributed to the presence of dark matter.”

Or one must assume that some basic fundamental principles of physics have hitherto been incorrectly understood. “The only solution would be to reject Newton’s classical theory of gravitation,” adds Kroupa. “We probably live in a non-Newton universe. If this is true, then our observations could be explained without dark matter.” Such approaches are finding support amongst other research teams in Europe, too.

It would not be the first time that Newton’s theory of gravitation had to be modified over the past hundred years. This became necessary in three special cases: when high velocities are involved (through the Special Theory of Relativity), in the proximity of large masses (through the theory of General Relativity), and on sub-atomic scales (through quantum mechanics).

Source: Eurekalert. The relevant papers are available here and here.

May 10, 2009April 26, 2016 by Anne Minard

Caltech Observatory Dismantled So Others Can Rise

Caltech has announced it will begin decommissioning the Caltech Submillimeter Observatory (CSO) in Hawaii starting in 2016.

Caltech says the 23-year-old telescope is being replaced by the next generation of radio telescope, the Cornell Caltech Atacama Telescope (CCAT), to be located in Chile.

“The timing of this works very nicely,” says Tom Phillips, director of the CSO and Altair Professor of Physics in Caltech’s Division of Physics, Mathematics and Astronomy. “The international community of astronomers that rely on CSO will have a seamless transition as CCAT comes online just as CSO is decommissioned.”

Located near the summit of Mauna Kea, the CSO began operation in 1986.

The CSO’s 10-meter radio telescope was designed and assembled by a team led by Caltech’s Robert Leighton and is considered one of the easiest telescopes to use for astronomical observations.

Work at the CSO has led to the detection of heavy water on comets, which has helped determine the composition of comets. It has also led to the observation of “dusty” planets–which optical telescopes are often unable to see–allowing astronomers a better picture of a planet’s composition.

“The CSO has a distinguished history of scientific achievement in Hawaii,” says Caltech president Jean-Lou Chameau. “The work done there has led to important advances in astrophysics and made future observatories, such as the CCAT, possible.”

Phillips said it costs about $3 million a year to operate the CSO — an amount that will be better spent on the new telescope. Besides, he said, “Caltech is a world leading research facility and it is not supportive of any activity not satisfying that criterion. The CSO does that today, but it won’t by 2016.”

Caltech operates the CSO under a contract from the National Science Foundation (NSF). Its partners include the University of Texas and University of Hawaii. The observatory has been a host for many scientists worldwide. As part of its mission, observatory time is shared among University of Hawaii researchers, Caltech, the University of Texas, and international partners.

Eleven staff members currently work at the Hilo, Hawaii offices of the observatory while about eight staff members work at Caltech’s Pasadena campus.

When CCAT comes online in the next decade, it will be used to address some of the fundamental questions regarding the cosmos, including the origin of galaxies and early evolution of the universe; the formation of stars; and the history of planetary systems.

CCAT is a joint project of Cornell University, Caltech and its Jet Propulsion Laboratory, the University of Colorado, a Canadian consortium including the University of British Columbia and Waterloo University, a German consortium including the University of Cologne and the University of Bonn, and the United Kingdom through its Astronomy Technology Centre at Edinburgh. More than twice the size of the CSO, the 25-meter CCAT telescope will be located in the high Andes region of northern Chile.

Source: Caltech. The observatory website is here.

May 8, 2009December 24, 2015 by Fraser Cain

Virgo Supercluster

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It’s time to expand your mind and consider the largest structures in the Universe: vast collections of galaxies known as superclusters. There’s really nothing bigger in the Universe. The supercluster we live in is known as the Virgo Supercluster. It’s an enormous collection of more than a million galaxies, stretching across a region of space 110 million light-years across.

Our Sun is just one member of the Milky Way, and the Milky Way is part of a collection of galaxies known as the Local Group. This contains three large spiral galaxies: the Milky Way, Andromeda, and the Triangulum Galaxy, as well as a few dozen dwarf galaxies. The Local Group is just one member of the Virgo Cluster. This is a collection of 1200-2000 galaxies that stretch across 15 million light-years of space. And then, the Virgo Cluster is just one cluster in the Virgo Supercluster.

Although astronomers recognized that we were in a supercluster of galaxies in the 1950s, it wasn’t until the 1970s that astronomers actually mapped out the Virgo Supercluster’s shape; it has a flattened disk, somewhat like our galaxy itself. Our Virgo Cluster is actually an outlying group of the Virgo Supercluster.

The Virgo Supercluster is just one of millions of superclusters across the Universe. From the largest scales, they’re arranged in long filaments and walls surrounding even large voids of space where there are almost no galaxies at all.

We have written many articles about galaxies for Universe Today. Here’s an article about how the Universe isn’t expanding uniformly.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 8, 2009December 24, 2015 by Fraser Cain

Virgo Cluster

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The key force in astronomy is gravitational attraction. Planets orbit stars, and stars are part of galaxies. But even galaxies come together into groups with dozens of members. One of the larger structures in the Universe are galaxy clusters; collections of thousands of galaxies. And our Milky Way is no exception. We’re a part of a much larger structure known as the Virgo Cluster.

The Virgo Cluster contains about 1300-2000 member galaxies, which are all connected together by mutual gravity. Astronomers estimate that it contains a total mass of about 1.2 quadrillion times the mass of the Sun. It covers a total volume of space with a diameter of 15 million light-years across.

Just like it’s name, the galaxies in the Virgo Cluster are mostly located in the constellation of Virgo, and one of the largest members of the cluster is the giant elliptical galaxy Messier 87. This monster is thought to have about 2.7 trillion solar masses all on its own.

The Virgo Cluster is just one member of an even larger structure: the Virgo Supercluster. This supercluster, also located in the constellation of Virgo is thought to have more than a million member galaxies, and stretches across a region of space 110 million light-years in size.

Superclusters are the largest structures in the Universe, and there are thought to be millions of them across the entire Universe. From the largest scales, these superclusters are stretched out into long filaments with large voids in between them. Seem from the longest distances, they would look like foam bubbles.

We have written many articles about galaxies for Universe Today. Here’s an article about the Virgo Cluster sucking in a distant galaxy, and here’s another article detailing a study of the Virgo Cluster.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 8, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – May 8-10, 2009

Greetings, fellow SkyWatchers! Are you ready for the weekend? Then step outside and see if you’re able to spot Mercury as it begins retrograde. Celebrate the “Full Flower Moon” and Mother’s Day with some very special insights into a very special mother. Maybe you can give your mother the “String of Pearls” or perhaps just some glittering jewels of some very fine double stars? No matter what you choose to do, there’s always something new to find and explore. Follow me…

Friday, May 8, 2009 – As the skies darken this evening, scan the western horizon for Mercury. Just beginning its 2009 Mercury retrograde motion, it won’t be long before it slips back into the glare of the Sun!

Tonight the Moon will command the sky. Why not take this opportunity to have a look at a very curious feature? Scan the lunar surface just a little southeast of the gray oval of Grimaldi. The area we are looking for is called the Sirsalis Rille , and on an orb devoid of magnetic fields—it’s magnetic! Like a dry riverbed, this ancient ‘‘crack’’ on the surface runs 480 kilometers along the surface and branches off in many areas. The Sirsalis Rille is a favored area for lunar geophysics. Although no complete explanation yet exists for its magnetic properties, it’s believed the Rille could be the surface remains of a channel that once fed magma to Oceanus Procellarum. If you look carefully, you will notice that Sirsalis crosses the ejecta of the Mare Orientale impact, leading the scientists to believe it formed after the Imbrium Basin.

There is also a theory that the Sirsalis Rille could be a graben—an impression left when two parallel faults shift. This is in line with the theory that rising magma may have disturbed the crust. Although there’s no firm evidence of volcanic activity, solidified magma under the surface may account for Sirsalis’ magnetic properties.

Lastly, there should be some fascinating effects at sunrise over Darwin, including an unexplained ‘‘string of pearls’’ effect, a possible result of light passing through a series of sharp, steep ridges. Keep a close watch on crater Darwin if you are watching as the Sun rises over the rim. Note what you see, including exact time the effect was spotted, the date, and your location. If you are interested in contributing, send your observing reports to the Association of Lunar and Planetary Observers (ALPO).

Saturday, May 9, 2009 – On this date in 1962, Massachusetts Institute of Technology (MIT) scientists bounced a laser beam off the Moon, which illuminated an area with a diameter of 4 miles! The ‘‘Luna See’’ project was a ruby optical laser radiating pulses of approximately 50 joules energy for half a millisecond. It was transmitted through a 1200 Cassegrain telescope and detected with a 4800 Cassegrain. It proved laser light could travel through space!

Tonight is the ‘‘Full Flower Moon.’’ Earth is awakening again! Agricultural literature refers to it as the ‘‘Full Corn Planting Moon,’’ or the ‘‘Milk Moon.’’ No matter what it’s named, Moonrise is majestic to watch. Participate in a Lunar Club Challenge and do some outreach work by demonstrating “Moon Illusion” to someone. We know it’s purely psychological and not physical, but the fact remains that the Moon seems larger on the horizon. Using a small coin held at arm’s length, compare it to Luna as it rises, and then again as it seems to “shrink” as it moves up! You’ve now qualified for extra credit…

Try using colored or Moon filters to look at the many surface features that throw amazing patterns across its surface. If you have none, a pair of sunglasses will suffice. Look for things you might not ordinarily notice, such as the huge streak emanating from crater Menelaus, the pattern projected from Proclus, or the bright tiny dot of little-known Pytheas north of Copernicus. It’s hard to miss the blinding beacon of Aristarchus! Check the southeastern limb, where the edge of Furnerius lights up the landscape… or how a nothing crater like Censorinus shines on the southeast shore of Tranquillitatis, while Dionysus echoes it on the southwest. Could you believe Manlius just north of central could be such a perfect ring, or that Anaxagoras would look like a northern polar cap? Although it might be tempting to curse the Moon for hiding the stars when it’s full, there is no other world out there that we can view in such detail… even if you just look with your eyes!

Sunday, May 10, 2009 – Today we celebrate the birth of Cecilia Payne in 1900 (and another female astronomer you just might know a little more than fifty years later). Payne was the first to apply the laws of atomic physics to study the temperature and density of stars. It was a difficult time for female astronomers, and she had quite a time getting her peers to take her work seriously. (And it’s still a difficult time for female amateurs – so hang tough.) Payne proved that hydrogen and helium are the two most common elements in the universe and, with the later help of Fred Hoyle, proved that our Sun is 99% hydrogen and helium.

Before the Moon rises, take a look at the constellation of Leo and its brightest stars. Our first destination is 85 light-year-distant Regulus. As the 21st brightest star in the night sky, 1.35-magnitude Alpha Leonis is a helium star about 5 times larger and 160 times brighter than our own Sun. Speeding away from us at 3.7 kilometers per second, Regulus is also a multiple system whose 8th magnitude B companion is easily seen in small telescopes. Regulus B is also a double, with a magnitude 12 dwarf companion of uncertain type. There’s an additional 13th magnitude star in this grouping, but it’s probably not associated with Regulus, since the ‘‘Little King’’ is moving toward it and will be very close to it in 800 years.

About a fist-width northeast of Regulus is 2.61-magnitude Gamma Leonis. Algieba is a very fine double star, but difficult to see at low power, since the 90 light-year-distant pair is bright and close. Separated by about twice the diameter of our own Solar System, the gap between Algieba and its companion is slowly widening! Another two finger-widths north is 3.44-magnitude Zeta. Aldhafera is about 130 light-years away and also has an optical companion—35 Leonis. Remember this binocular pair, because they’ll lead you to galaxies later! Before we leave, look east for 3.34-magnitude Theta. Mark this one in your memory, because Chort and 3.94-magnitude Iota to the south serve as markers for a galaxy hop! Last is easternmost 2.14-magnitude Beta. Denebola is the ‘‘Lion’s Tail’’ and has several faint optical companions.

Now watch the Moon… because for some areas Antares is about to be occulted!

As we’re watching, let’s take just a moment a give thanks for our mothers and the roles they can play in our lives. Did you know Johannes Kepler’s mother, Katharina, was the one who inspired him? To rather paraphrase his story, Johannes’ father was a mercenary soldier and left him and his mother when he was a young child. His mother supported them both by working as a waitress at the family inn and put the very religious and mathematically talented young Johannes through seminary school on her own. It was his mother who took him to to watch the great comet of 1577 and an eclipse of the Moon – inspiring his love of astronomy. After he graduated, he became an assistant to Tycho Brahe, supported Copernican theory and worked with Galileo. While Kepler was working on his “Harmony of the World” his 70 year old mother was charged with witchcraft because she collected herbs, made potions and understood astrology. Isn’t that about the way it went for anyone back then who was interested in the stars? Anyhow, Kepler got a lawyer and managed to save her from the fate of the aunt who raised Katharina. She was also burned at the stake for being a witch!

Until next week? Don’t collect any herbs unless they’re legal… And keep on reaching for the stars!

This week’s awesome images are (in order of appearance): Sirsalis Rille and region (credit—Alan Chu), Project Luna See (credit—courtesy of MIT Museum), Full Moon (credit—NASA), Cecilia Payne (historical image), Stellar magnitudes in Leo (credit—NASA) and Katharina Kepler (historical image).

May 8, 2009December 24, 2015 by Anne Minard

‘Astro-comb’ Will Aid Search for Extra-terrestrial Planets

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As the race ramps up to find Earth-like planets around other stars, lasers are a viable option.

That according to researchers at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who have created an “astro-comb,” a sort of calibration tool based on wavelengths of light, to pick up minute variations in a star’s motion caused by orbiting planets.

In most cases, extrasolar planets can’t be seen directly—the glare of the nearby star is too great—but their influence can be discerned through spectroscopy, which analyzes the energy spectrum of the light coming from the star. Not only does spectroscopy reveal the identity of the atoms in the star (each element emits light at a certain characteristic frequency), it can also tell researchers how fast the star is moving away or toward Earth, courtesy of the Doppler effect, which occurs whenever a source of waves is itself in motion. By recording the change in the frequency of the waves coming from or bouncing off of an object, scientists can deduce the velocity of the object.

Though the planet might weigh millions of times less than the star, the star will be jerked around a tiny amount owing to the gravity interaction between star and planet. This jerking motion causes the star to move toward or away from Earth slightly in a way that depends on the planet’s mass and its nearness to the star. The better the spectroscopy used in this whole process, the better will be the identification of the planet in the first place and the better will be the determination of planetary properties.

Right now standard spectroscopy techniques can determine star movements to within a few meters per second. In tests, the Harvard researchers are now able to calculate star velocity shifts of less than 1 m (3.28 feet) per second, allowing them to more accurately pinpoint the planet’s location.

Smithsonian researcher David Phillips says that he and his colleagues expect to achieve even higher velocity resolution, which when applied to the activities of large telescopes presently under construction, would open new possibilities in astronomy and astro physics, including simpler detection of more Earth-like planets.

With this new approach, Harvard astronomers achieve their great improvement using a frequency comb as the basis for the astro-comb. A special laser system is used to emit light not at a single energy but a series of energies (or frequencies), evenly spaced across a wide range of values. A plot of these narrowly-confined energy components would look like the teeth of a comb, hence the name frequency comb. The energy of these comb-like laser pulses is known so well that they can be used to calibrate the energy of light coming in from the distant star. In effect, the frequency comb approach sharpens the spectroscopy process. The resultant astro-comb should enable a further expansion of extrasolar planetary detection.

The astro-comb method has been tried out on a medium-sized telescope in Arizona and will soon be installed on the much larger William Herschel Telescope, which resides on a mountaintop in the Canary Islands.

Preliminary results from the new technique were published in the April 3, 2008 issue of Nature. The Harvard group will present the most recent findings at the 2009 Conference on Lasers and Electro Optics/International Quantum Electronics Conference, May 31 to June 5 in Baltimore.

Source: Eurekalert